Thames, the most important river of Great Britain, flows east-south-east across the south portion of the country. Its four head-streams—the Thames or Isis, Churn, Coln, and Leach—rise on the south-east slope of the Cotswold Hills, the upper part of the main stream being often called Isis (a quasi-classical form of Ouse) and not Thames until after it receives the Thame near Dorchester. The Thames or Isis flows east-north-east for about 35 miles, when, curving south-east, it passes Oxford, and flows on to Reading, where, after receiving the Kennet from the west, it again changes its course; and with a generally eastward course it passes Windsor, Eton, Teddington (the lowest of thirty-three locks between here and Oxford, and the highest point to which the tide ascends), Richmond, London, Woolwich, and Gravesend, a few miles below which it expands into a wide estuary, and enters the North Sea. On its tidal estuary, and on the fact that like most British rivers it has no delta, depends the river's importance as a navigable waterway; the navigation is, however, somewhat impeded by what has been called a 'submarine delta'—banks formed of river sediment. From Lechlade to the Nore the direct length is 120 miles, and with the windings may be 250 miles (112 from Oxford to London Bridge); the area of its basin is 6100 sq. m. Throughout the greater part of its course it forms the boundary-line between several of the southern counties. Passing Cricklade, it forms part of the northern boundary of Wilts, and below this point it separates the counties of Oxford, Buckingham, Middlesex, and Essex on the north from those of Berks, Surrey, and Kent on the south, except certain outlying bits of some of these counties. Its chief affluents are the Windrush, Cherwell, Thame, Colne, Lea, and Roding, on the left; and the Kennet, Loddon, Darent, Mole, Wandle, and Medway, on the right bank. At London Bridge the width of the river is about 290 yards; at Wool- wich, 490 yards; at Gravesend Pier, 800 yards; three miles below Gravesend, 1290 yards; and at its mouth, between Whitstable and Foulness Point, about 8 miles below the Nore, it is 18 miles across. At the Nore Light, the commonly reputed mouth of the Thames, the breadth is nearly 6 miles. The river is navigable for barges to Lechlade, and it is connected with several important canals, by means of which it maintains communication with the west and south coasts, and with the interior of the country. Vessels of 800 tons can reach St Katharine's Docks; much larger ones can ascend to Blackwall, 6 miles below London Bridge; and the largest sea-going steamers reach Tilbury Docks, 26 miles below (see DOCKS). The part of the river immediately below London Bridge is called the Pool; and the part between the Bridge and Blackwall is called the Port. Two embankments have been formed, one since 1864 on the north shore from Blackfriars Bridge to Westminster, and one since 1866 on the south shore from Westminster Bridge to Vanxhall. The river supplies London with much of its drinking-water, and carries most of its sewage to the sea (see WATER-SUPPLY; and SEWAGE, Vol. IX. p. 341). Some of the great bridges which span the river at London are described at BRIDGE.
Though the lower Thames has been converted into a sewer, in virtue of this same part of its course the river ranks as the chief commercial highway of the world. Above London the scenery is rich and beautiful, though not romantic or picturesque, the numerous islands or eyots lending a peculiar charm. The Thames is the best beloved of English rivers for those who boat for pleasure. For boat-racing, it divides the honours with the Tyne (see ROWING); the Thames watermen are renowned in song and story. Since Spenser's days 'the silver-streaming Thames' has been sung by England's poets; Herrick calls it 'Silver-footed Thamesis'; Denham's apostrophe (quoted at DENHAM) has long been famous; and Pope has gracefully word-painted much of the scenery of its banks. It was (now alas! long since) famous for its salmon, as it still is for other anglers' fish; below London flounders and eels are still plentiful, while the whitebait is almost peculiar to the lower Thames.
The Thames has a copious bibliography of its own (comprising upwards of seventy entries in Anderson's British Topography and upwards of 150 in Notes and Queries for 1884). Many of these works are richly illustrated. Of comparatively recent ones may be mentioned that by Mr and Mrs S. C. Hall (1859; new ed. 1878), Robertson (1874), Huxley (Physiography, 1877), Farren (1881), Law (1881), George D. Leslie, R.A. (1881; new ed. 1888), Church (1885), Herring (1885), Cassell (Royal River, 1886), W. Black (Strange Adventures of a House-boat, 1888), Justin McCarthy and Mrs Campbell Praed (1890), Senior (1890), Mr and Mrs Pennell (1891); Wyllie and Allen, The Tidal Thames (1894); and the annual Dictionary of the Thames (since 1881), by Charles Dickens, junior.